rxse7en

I just finished installing and setting a replacement TPS in the '87 N/A, took the car out and it ran beautifully. After reading some posts on the ECU I decided to go ahead and reset it thinking it may need to "register" all of the mods and replacement parts I've put on. I took the car out again and now I find that I've reintroduced the 3800 rpm stumble I fixed months ago! I have to think that the hesitation is just a coincidence and that I may have knocked one of the MILLION grounds I placed in the engine bay!

So I pose these questions to you fellow readers:
1. What actually happens when resetting the ECU?
2. When reading resistance for the Boost Sensor ground—what points should I actually check with the DMM?

Thank you all!

B

TRURX7

Man, I feel for you. This problem sux big time. I used to have it and if it ever came back to me I swear I would not be happy. Yesterday, after I installed a capacitor, my 87 NA started running like a dream. Of course I reset the ecu right after installing the cap.

Good Luck M8
Horacio

rxse7en

Please explain the capacitor installation and why you did it.

B

rocketpower

How do you reset the ECU. I thought that the ECU reset itself and did not hold any codes on the 86-87.

Amur_

Yeah, no ****. I'd always heard that only the ECUs in FDs can be reset...

ttyl,
Amur_

TRURX7

Well its the third time I post it. But if its going to help another person possibly rid their car of the 3000rpm stumble. Follow this link:

https://www.rx7club.com/forum/showth...threadid=67519

The capacitor I have is wired through my stereo system. Basically the capacitor will do its job regardless of where you wire it, but it will do better if you wire it closer to what you want to get the most benefit out of it. The capacitor basically holds electrical charge (critical in high power subwoofer and also in our cases with critical engine components that arent getting voltage when they are pushed hard.) Running extra grounds works in the same concept of keeping the charging system healthy. I recommend extra grounds be run first before you invest in a capacitor and see if that gave you any results.

Wiring the capacitor: Basically its a no brainer, keep the capacitor mounted sturdy because if it shorts out, it will create an explosion. Most capacitors out there come with a resistor to help you charge it before you install it. If you are carefull, you can bypass it and follow the instructions with most electrical components and disconnect the battery ground before you do anything and reconnect the ground after you do anything. Dont place the capacitor in your engine compartment, place it in a safe place where nobody can tamper with it.

rxse7en

Thanks for the input Tru. I'm going to replace the current grounds with heavier gauge grounds and see if that fixes her. I still don't understand why the hesitation reappeared after months.

Icemark

TRURX7,

Your cap will only affect engine operation if you have either a bad alt or bad battery. The cars battery is nothing more than a giant cap, so if it's inductance is failing (like you have a bad cell or something)or the alt is not providing sufficent voltage, those would be the only reasons that the cap would help your car run, with the way you have described it wired.

A cap is not a band aid for all the electrical problems in a car unless the battery is failing. And then the proper new battery should be used.

gottadrive

so are you saying a new battery 'COULD' fix the 3800 hesitation?

Icemark

No I am saying that the cap will have no effect what so ever on the car if the alt and battery are in good operating condition.

The Cap only stores power that it can release as needed, just like the battery. So just adding a cap to the system can't fix anything if the battery is good.

I know that he says the cap solved his hesitation problem and fuel pump problems, but I doubt they really did. Simply coincidence. My experience shows that the 3800 hesitation is usually related to poor grounds, bad switches, or cold solder joints. I would not be surprised if his problems re-appear sometime in the next year.

Caps are used for three reasons in car audio

1, like he is doing to supply power for the stereo on quick demands. Although in the majority of car audio amps the internal power supplies also have sufficient storage built in and a cap does little. A cap can only help in this case if the battery is not big enough to provide storage for the demands of the electrical system.

2, for noise reduction. If a alt is leaking or is a poor design (like many of the bosch alts that allows AC to actually be introduced into the electrical system), a large enough cap will act almost like a rectifier to solve this.

3, to make money off of people that think it will make their car stereo louder/cleaner/better. If you look inside most car audio caps they are a lead weight and just enough plating to get the minimal storage spec. Most 1 farad caps cut open are 50% empty. This means they really don 't have instant transient response that if something in the car (namely the audio amps) needed voltage for.

DrunkenMaster

How do u Reset the ECU!?!?, and what good does it do ?

Icemark

This was something that was started with the OBD I cars. People found that resetting the ECU on the 90's and later cars often gave them proceived power gains and "adapted" the computer to any mods they may have made.

Unplug/disconnect the battery and then press the brake a couple of times.

Now on RX-7s I thought that it only helps the series 5 cars and later. Re-sets the 'puter to factory default. So if there are any mods made to the car, within 500 or so miles the computer re-adjustes to the mods and driving style.

Angel Guard Racing Team

All you need to do is adjust the tps. I built the little two bulb tool to get the tps adjusted and also pull codes from 86-88. It works just fine

TRURX7

Just wanted to let you guys know. After I installed the cap, I drove the car for 800 miles to NYC and just got back today. Guess what? The car NEVER once hesitated even with all the ups and downs as far as elevation on the way there. Pulled hard all the way average speed ~85mph =) I was a happy camper plus I didnt get a ticket and I got there and back in one piece.

The reason I chose to try a capacitor for fixing my problem was because: I had checked everything else that I could think of and what people suggested and nothing worked, After 3 months nothing seemed to fix the hesitations, slight improvement when using extra grounds from the battery, had a capacitor lying in the garage doing nothing but collecting dust.

[quote] 3, to make money off of people that think it will make their car stereo louder/cleaner/better. If you look inside most car audio caps they are a lead weight and just enough plating to get the minimal storage spec. Most 1 farad caps cut open are 50% empty. This means they really don 't have instant transient response that if something in the car (namely the audio amps) needed voltage for.
[quote]

I am sorry to tell you this, but capacitors do make a HUGE difference in car stereos, I just happen to be a professional car audio installer as well.



Good luck to yall.
Horacio

TRURX7

PS, after installing the capacitor I noticed the voltmeter on my dashboard stayed a lot closer to a healthy 14V (600watt stereo, low beams + high beams, blower motor on high). I have a brand new 8 year battery 900CCA and my alternator is putting out 80A.

I am not saying that this is THE FIX for the 3000rpm stumble, but it sure as hell worked for me.

Amur_

And after these posts I think I'll be slapping a cap in my FC soon, too.

Don't make me bust a cap in yo car!

ttyl,
Amur_

TRURX7

I want to apologize to Icemark. I am sorry for sounding like I am questioning your expertise on the subject.

Icemark

You don't have to apologize...You didn't offend me. This is an open forum and everyone's ideas are valued.

My only point that I thought I had made was that before you spend $50 to $100 on a cap, that you need to exhaust the other more common avenues.

I am glad that it appears that the hesitation is gone in your car after installing the cap. But lets do a little test before we claim it solves world hunger. Lets disconnect the cap in your RX-7 and see if the problem re-appears.

In the mean time I will throw back my spare '338 ECU that I know has a cold 3800 hesitation problem (because it did when I tested it and I haven't bothered to re-solder the plugs on it like I did my first one) and a spare 1 farad cap (as some know I worked quite a while doing car audio electronics and performance, so I have a couple of caps laying around) this weekend and see if solves the issue.